No, we went through the guesses, then went through the episode list and narrowed it down. There are only so many episodes with practical effect explosions in them, and it looked like an earlier episode.

Sorry about that. Many of the two-parters' first part is just the episode title, without the "Part I"... (ie: "Time's Arrow" and "Redemption." I realize that this is not the case with the Gambit two-parter, but I thought it was. My bad!